This article investigates gender differences in 181 gifted and 181 average-ability sixth graders in achievement, academic self-concept, interest, and motivation in mathematics. Giftedness was conceptualized as nonverbal reasoning ability and defined by a rank of at least 95% on a nonverbal reasoning subscale of the German Cognitive Abilities Test. Mathematical achievement was measured by teacher-assigned grades and a standardized mathematics test. Self-concept, interest, and motivation were assessed by questionnaire. In both ability groups, boys earned significantly higher test scores but there were no gender differences in grades. Girls scored lower on measures of academic self-concept, interest, and motivation. Gender differences were larger in gifted than in average-ability students. Ability group differences for self-concept and interest were only found for boys in favor of the gifted. Results support the assumption that gender differences in self-concept, interest, and motivation in mathematics are more prevalent in gifted than in average-ability students.